6 
Research Bulletin No. 3 
regarding the amounts of available soil moisture as can be se- 
cured by an ordinary farmer using only bis eyes, his hands, and a 
spade or auger, is not so remarkable as it may at first appear. 
On the one hand, the direct determination of the nonavailable soil 
moisture is so tedious that in field studies, where a separate de- 
termination for every sample might be necessary, the amount of 
labor involved appears prohibitive. 1 On the other hand, experi- 
mental data on the relation of the nonavailable water to the 
hygroscopic coefficient are very scanty and there has never been 
a general recognition of the latter as equivalent to the nonavail- 
able moisture. The general failure to recognize that differences 
in moisture content which are very apparent while the samples are 
being collected are not to be detected from the tabulated percent- 
ages of total water is probably due to the general practice of 
having assistants or laborers attend to the collecting of the sam- 
ples. 
The lack of a general recognition of the importance of the de- 
termination of the hygroscopic coefficient is probably, however, 
due chiefly to the reaction from the old view of the practical im- 
portance to be attributed to the relative amounts of moisture 
which different soils, when dry, are able to absorb from the at- 
mosphere, a view which originated with Sir Humphrey Davy 
early in the nineteenth century and was fully accepted by the 
foremost investigators until 1875. The long acceptance of this 
erroneous view of the value of the hygroscopicity of soils was due 
to the prevailing opinion that the amount of water lost by trans- 
piration from a unit area of land was far in excess of the 
amount of water falling, as rain and snow, upon the same area. 
This loss had been calculated from pot experiments in which 
plants had at all times been kept supplied with an abundance of 
1 A good illustration of the variability of the soil of individual samples 
from foot to foot and from boring to boring is indicated in the following, 
which gives the hygroscopic coefficients of soil samples taken from dif- 
ferent fields at the same time or from the same field at different times 
on the H O Ranch, near Madrid, Nebraska: 
Depth 
No. 1 
No. 2 
No. 3 
No. 4 
No. 5 
No. 6 
No. 7 
No. 8 
No. 9 
No. 10 
No 11 
Feet 
1 
7.8 
8.5 
8 0 
7.5 
7 1 
7.4 
5.9 
8.5 
7.0 
5 3 
1 9 
2 
10 4 
9.8 
9.8 
10.5 
10 4 
6.1 
6 3 
10.2 
7.8 
5.1 
1.8 
3 
10.2 
9.8 
11.3 
9.2 
8 0 
7.0 
6.4 
12.4 
9.3 
3.3 
1 7 
4 
7.0 
8.3 
7.7 
6.9 
6.7 
7-2 
7.1 
13.1 
13.0 
3.0 
1.5 
5 
7.0 
6.9 
6.4 
6.6 
6.3 
7.1 
7.7 
12 2 
14 2 
3.0 
1.8 
6 
7.8 
7.4 
6.3 
6.9 
6.0 
9.1 
9 3 
9.0 
12 8 
1 9 
1.9 
7 
6.9 
5.9 
4.0 
4.1 
9.1 
11 5 
9.4 
2.7 
17 
8 
5.1 
3.9 
9.1 
9.9 
9.2 
2.2 
1 8 
9 
5 9 
2 9 
7.7 
9 0 
9 2 
3 8 
1 5 
